1. Field of the Invention
The present invention relates to a dry etching apparatus for performing dry etching of a workpiece such as a semiconductor wafer and, more particularly, to a dry etching apparatus utilizing magnetron discharging.
2. Discussion of the Background
In recent years, a manufacturing technique of semiconductor integrated circuits has been developed, and a semiconductor integrated circuit incorporating individual elements having a size on the order of submicrons, i.e., an LSI (large scale integrated circuit), has recently been manufactured on an experimental basis. In recent studies of manufacturing techniques of LSIs, a large number of trenches are formed in a silicon substrate, and an insulating material is buried therein to isolate individual elements, or after a thin oxide film is formed on the inner surface of each trench, a conductor serving as an electrode is buried in the trench to form a capacitor of a MOS (metal oxide semiconductor) structure.
When an LSI is manufactured using the above-mentioned techniques, deep trenches having a small opening width, i.e., having a large aspect ratio (depth of trench/opening width) must be formed in a silicon substrate.
After a silicon oxide (SiO.sub.2) film as a mask is formed on a silicon substrate, trenches having a large aspect ratio are formed by reactive ion etching (RIE). However, in the conventional RIE, an etching speed is very slow, i.e., about 0.1 m/min, and becomes slower as the opening width of the trench becomes smaller.
In the trench formed by the conventional RIE, a portion of the inner wall surface near the opening is scooped out, and another portion of the inner wall surface near the bottom portion is etched to be a tapered surface. Thus, it is difficult to form a straight inner wall surface of the trench. The reason why the etched portion or the tapered surface is formed is that a large number of reactive ions obliquely bombard the masked surface of the silicon wafer.
Furthermore, in the conventional RIE, high-energy reactive ions are radiated onto a silicon wafer. Elements already formed on the silicon wafer are damaged by the reactive ions.